1. Field of the Invention
The present invention relates to an inspection system for inspecting a power train employed in an automobile or the like, to a power train including such an inspection system, and to a control unit for the power train. The term “power train” as used herein is intended to include an automatic transmission (hereinafter also referred to as an A/T), a continuously variable transmission (hereinafter also referred to as a CVT), a semiautomatic transmission, an electric motor serving as a drive of a vehicle, an engine and an electric motor installed in a hybrid vehicle, and the like.
2. Related Art
U.S. Pat. No. 5,456,647 discloses driving an engine to rotate a turbine and to operate actuators of frictional engagement elements with rotational speed of the engine being held constant so as to learn characteristics of all the frictional engagement elements, wherein strokes of the actuators are determined upon detection of a drop in rotational speed of the turbine where frictional engagement elements are regarded as having reached a torque-transmitting state, and wherein values of the strokes are stored in memory for future use in gearshift control of the A/T.
Japanese Patent Publication No. 2001-502405 discloses a method including the steps of determining the time required for filling a clutch actuator with oil, pressure of the oil, and reaction time from change of an input rotational speed, output rotational speed, input torque, output torque, and time of the final bench test of an A/T. The disclosed method further includes correcting the timing of piston stroke pressure, timing for holding pressure, and timing of switching pressure, storing the corrected values in memory during the bench test, and causing a control unit of the A/T to read the corrected values and to use the corrected values for gearshift control of the A/T after the A/T has been installed in the automobile.
German Patent Application Laid-Open No. 19-943,069 discloses a control unit which measures and detects pressure tolerance in an operational range, derives a correction value as deviation from a reference characteristic curve, and writes the correction value into memory.
In the automatic transmission control system disclosed in U.S. Pat. No. 5,456,647, after the automatic transmission has been fabricated, all the frictional engagement elements are tested and values thus obtained are stored in memory. Hence, in order to learn the characteristics of all the frictional engagement elements, the same operation has to be repeated many times. This creates a problem because it takes a long time to finish final inspection of the newly assembled automatic transmission.
Further, since final inspection of the automatic transmission is conducted with the A/T installed in the vehicle, the automobile plant requires space devoted to learning the characteristics of the frictional engagement elements. Even if the charcteristics of the frictional engagement elements are learned before the A/T is installed in the vehicle, a dedicated space is required.
Japanese Laid-Open Application No. 2001-502405 discloses such learning implemented in the final bench test with of the newly fabricated automatic transmission before installation in an automobile, a problem more or less similar to that described in connection with the aforementioned U.S. Pat. No. 5,456,647 is encountered.
German Patent Application Laid-Open No. 19943069 discloses an automatic transmission control unit that can appropriately correct characteristic values at certain points but not at other points. Thus, this control unit cannot always control the A/T with high precision.